1. Field of the Invention
The present invention relates to metering a length of duct from a flexible container retaining the duct in a longitudinally compressed state, and more particularly to a choker for configuring the longitudinally compressed duct and the flexible container to generate tension in a portion of the container corresponding to a longitudinal expansion force of the duct, wherein the tension resists longitudinal expansion of a portion of the longitudinally compressed duct in the flexible container.
2. Description of Related Art
Flexible duct is used for the transfer of air, heated air or cooled air or other gases. Typically the flexible duct is designed for low-pressure usage, for example about 3 to 5 inches of water pressure.
The flexible duct is normally composed of an inner liner or core reinforced by a helical strand such as metal or plastic, a thick layer of flexible insulation such as fibrous glass around the liner, and a flexible plastic, i.e. polymeric, jacket surrounding the insulation.
Shipping, handling and storage costs, as well as installer convenience are substantially improved by longitudinally compressing the flexible duct into a container, typically an elongated box, having a length only a fraction of the initial (free) length of the duct.
However, upon opening the box to access the longitudinally compressed duct, the entire length of the compressed duct expands, thereby rendering it difficult to retain the unused length of duct within the box. For example, if a 10 foot length of duct were needed, the box is opened and the duct is extended to the full 25 foot length, wherein it the desired 10 foot section is then cut. Recapturing the remaining 15 feet of duct into the box is a difficult and time-consuming operation for the individual installer. Further, for longitudinally compressed duct shipped in a flexible container, such as a bag, reinsertion of the longitudinally expanded (relaxed) duct is particularly cumbersome.
Therefore, the need exists for a method of selectively metering a desired length of extended duct, without requiring or allowing the entire length of longitudinally compressed duct to expand. The need also exists for a metering system that can be employed without requiring significant additional material costs. In addition, the need exists for a metering system that can be readily utilized at job sites without requiring additional tools. A further need exists for a metering system that can effectively retain an unused length of the longitudinally compressed duct in the original container, wherein such retained duct remains substantially in the compressed state.